Invert document colors (night mode)

[PeterNerlich]

[Feature Request]

Configuration:

• Web browser and its version: Chromium 57.0.2987.98
• Operating system and its version: Elementary OS Loki (elementary 0.4, 64-bit)
• PDF.js version: 1.6.293
• Is an extension: Yes

The systems default PDF viewer has this handy feature inverting the colors of the document, which I use all the time as it is considerably more convenient, especially at night. To my understanding, this should be very easy to implement, as it required no more than applying filter: invert(); to the .pdfViewer .page and maybe inverting the border image again.
It would also be handy to have the keyboard shortcut [Ctrl] + [I] for it, as it is used in the systems viewer.

[Snuffleupagus]

Closing as duplicate of issue #2071 (and #2163).

[alexchandel]

Please re-open. Night mode refers specifically to @media (prefers-color-scheme: dark) { ... } CSS, which is not the same as the user generically changing text/background colors.

[silgon]

Please re-open. Something like [Ctrl] + [I] would be really neat.

[let-def]

Thanks for the CSS rule. Since it seems this feature is not going to make it to PDF.js anytime soon, I saved it as a bookmarklet. If anybody is interested:

javascript:(function(f){if(f.cssRules.length)f.deleteRule(0);else f.insertRule('.pdfViewer .page{filter:invert();}');})(window['_pdfsty']=window['_pdfsty']||document.head.appendChild(document.createElement('style')).sheet))

It creates a new stylesheet element with the right rule, and toggle it (removing or re-adding it) if applied again.